How to judge the bioload on an aquarium? - The Planted Tank Forum
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post #1 of 6 (permalink) Old 03-12-2006, 06:56 PM Thread Starter
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How to judge the bioload on an aquarium?

How do you know how to judge what is a 'light' or 'high' bioload on an aquarium?

Granted, with smaller tanks (29gal & 20 gal) Having mulitple large schools of fish is out of the question, but I enjoy both my guppies and my neons, each share a different portion of the tank. In the 20 Gal the rasboras and the shrimp and the cory cats all share differnt aspects of the tank..

I enjoy the 29 gal, it looks as if it has a fairly decent bioload.

11-12 neons (cant ever get the still long enough to actually count them)
5 adult guppies, 20 2 month old juveniles
2 head & taillight tetras.

but sometimes I would like to expand my school of neons to about 20, but I am afraid of pushing the bioload of the aquarium.

The 20gal has 5 harlequin rasboras, 3 cory cats, 6 ghost shrimp (they were cheap and I am waiting on cherries to breed).

I would like to expand this to about 18 rasboras, 6-10 cory cats... but again.. bioload questions.

Also, I wonder if the fish would be comfortable with that many fish?

§ Will work for good water and co2. §
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post #2 of 6 (permalink) Old 03-12-2006, 11:10 PM
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Good that you're thinking of load both in terms of water pollution and fish stress. If you have lots of happy plants uptaking ammonia, you can get away with more crowding, as long as it doesn't get to the point that the fish start to feel crowded. What you envision for the 20 sounds like it might be pushing it, so you'll definitely want lots of plants. If you can leave a good sized open area, your Rasboras should school nicely. Your guppy population will continue to expand in the absence of a predator fish, so I'd go easy on adding any additional fish to the 29. If you really want to know how many neons you have, a photo might help. Use flash to freeze them. It will look terrible, but you should be able to get a count. Remember, plants plants plants. Short of plants, filter filter filter.
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post #3 of 6 (permalink) Old 03-12-2006, 11:16 PM Thread Starter
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Lots of plants.. pressurized CO2... eheim 2213 filter... So I think im doing well on taking care of filtration and water issues.

I change 5 gallons of water per week in each aquarium. (i have a 5 gallon bucket that i have to go get water that is suitable for the aquariums, so,.. 5 gallons at a time is about all I can really do)

I counted the neons, and there is 11.

With the fish crowding problems, I think that fish that like to school (Rasboras, Neons) Would be less stressed with more of their own kind, no?

§ Will work for good water and co2. §
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post #4 of 6 (permalink) Old 03-13-2006, 12:52 AM
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its pushing it a it but if you keep great filtration up and keep close eye on the fish it can be done. i pushed my 10g at one time with 2 full grown blue rams 4 full grown cories 2 full grown otto's and 3 juvies and some shrimp+ snails... the sky is the limit as long as you keep up the wc and the filtration more plants the better also! Good luck!

as for bioload a good guideline is about 1inch fish per gallon Give OR Take. thats a high estimation and especially with planted tanks. shrimp dont really count as bioload either unless you have a ton. some people have had 500+ in a 10g tank.

the important thing is to watch the fish.
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post #5 of 6 (permalink) Old 03-13-2006, 05:38 AM
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I remember years ago when I first got into the hobby visiting an Angle breeder at his house. He had a 55g with over 80 Angles that were the size of a half-dollar coin not including fins.

This was way before power filters or sumps so he was using an UGF. Having the 1-inch of fish per gallon rule already cemented into my skull, I was floored. I will never forget his answer when I asked, “how?”

“You can keep about as many as you want as long as you do enough water changes.” For him that was 20% every day. I still wouldn’t do it today, even if I had the time, but I know he did it for years.

The 1-inch of fish per gallon rule is still a good general guide, but it is very flawed. First, it outdates today’s technology. Second, it requires a lot of common since. A 1-inch neon tetra is obviously not the same as a 1-inch Puffer, which isn’t the same as a 1-inch Tiger Barb. Then you go into fish that are more sensitive to bio-loads than others, tank height/width, how often or how much the fish are feed, etc.

Today I don’t really follow any set rules. I let the tanks inhabitants and the water chemistry tell me when its full. I keep a close eye on water chemistry, algae growth, fish behavior, etc. I then balance that out with how often I know I will do water changes.

My current 29g setup.

6 Tiger Barbs
3 Emerald Cories
3 Cardinal Tetras
2 Dwarf Gouramis
2 Blue Rams
1 Betta

Some people would say that was 29 inches of fish, but I see it as 38 inches of fish and overstocked any way you look at it. However, the fish are happy, the plants are happy and the water chemistry is optimal as long as I maintain my 25% mid-week WC and my 40% weekend deep clean with WC.

29g Planted
10g Planted
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post #6 of 6 (permalink) Old 03-13-2006, 08:30 PM
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I'd say that the 1 inch per gallon rule is very, very general. It simply doesn't take into account the real biomass of a fish (weight). The classic example is that you could easily keep 10 inch long neons in a 10 gallon tank, but you can't keep a 10 inch oscar in the same tank. For any given species, if the fish doubles in length, it is actually 8 times the biomass.

I think a better rule would be that for small fish (less than 2 inches), 2 inches of fish per gallon is fine. For medium sized fish (2-5 or so), 1 inch per gallon. For large fish (5+ inches), figure only 1 inch for every two gallons. And I think this would have to be even further modified for real monsters.

But I'm also one who errs on the side of caution with stocking levels. And having a lot of plants certainly influences things.

Solace, looking at your tanks, I'd say the 29 is okay where it is. But I wouldn't go any further. Especially not with guppies and their breeding tendencies (suggestion: put in a dwarf cichlid for population control). As for the 20, I'd suggest a dozen rasboras and 6 cories. So both of them are happy with their school.
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